Class E Newbie - Intro and Questions

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Class E Newbie - Intro and Questions

Postby JT - W6FO » Thu Jul 14, 2005 5:01 pm

Hey everyone.

I've always wanted to homebrew my own stuff but have always been too intimidated or down right lazy. However, with my ever growing interest in AM, building my own gear is almost necessary and a prerequisite, in my mind, for true operating in this mode. Not to mention the fact that premanufactured equipment usually leaves me feeling cheated, dissapointed, and, often times, down right pissed off when I look at how much I've spent for things such as poor craftsmanship, features I will never use, or features not present that I need. Although I love the "glow" and nostalgia of tube rigs, Class-E seems to be of more interest to me from a building standpoint.

Therefore, I'm going to make an honest attempt at building the 350W 6-MOSFET transmitter here on QIX's site. I also have Class H Modulator/PS PCB's coming from KD1J. I am really inspired by the clean, and simple looking, assembly work by those such as K1KBW and K6JEK and hope to make my work at least half as good looking as these. If I am successful with this, I hope to then attempt a modularized RF amp similar to KBW's recent rig.

I am sure I will be full of questions as I start collecting parts and begin construction and hope everyone will have the patience to help me along or at least just listen.

That said, I'm going to need a dual-trace scope on my bench for this work and wondering if anyone has any suggestions on particular models I should be looking for. Would your typical $50 hamfest scope work for this kind of work?

Thanks guys.

73

JT - W6FO
JT - W6FO
 
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Postby W1DAN » Fri Jul 15, 2005 9:10 am

Hi JT and welcome to the forum!

There are many scopes that will do the job. I use an old Tektronix 466. The 465 is also a very good one. To me an extremely important part of your scope is the probe. Get a couple of good ones (the old P6105? is a fine one). These may cost a couple of hundred dollars if you buy them new. Hopefully they will come with the scope.

There are many people here on the forum who would be glad to answer questions and help you on. Some people may even have parts that you may need.

I have built the 6 FET QIX design..a great design! The Class H modulator is probably a lil easier to build than the PDM modulator.

One change I am very happy about...I split my 6 FET deck into a push pull group of three each. So I have two input transformers (out of phase) and output transformers to re-combine the outta phase signal back. The benifit is a closer to sine wave output and the amp does not work as hard.

I have made a fully modulated 400 watt carrier at times (that pushes the limit).

Do not be scared of building one...the worst thing to happen is blown FET's and caps. I am having so much fun running my rig. It was worth the effort to build it, and I consider this to be a high point in my ham career.

Let us know how we can help!

73,
Dan W1DAN
http://www.dbaudio.net
hroman@ix.netcom.com
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Postby JT - W6FO » Fri Jul 15, 2005 4:33 pm

Thanks for the welcome.

After some discussion with Steve QIX, I've decided to build a 5 MOSFET balanced rig from the start. Bunch of MOSFETs are on the way from Steve. I'm still planning on Kevin's (KD1J) Class H modulator/power supply boards.

73

JT - W6FO
JT - W6FO
 
Posts: 7
Joined: Thu Jul 14, 2005 4:16 pm
Location: Canton, GA

E-rig

Postby Brent » Wed Oct 19, 2005 2:29 pm

JT...the KD1J boards are no longer available, but WA1QIX will be making the class-H modulato boards available very soon. As far as the over-current protection board, they are very simple to construct.

I recomend a 10 fet rf deck design over the 6 fet. Two 5 fet modules will provide lower 2nd order harmonic distortion characteristics. Steve will be updating the site in the future to reflect the 10 fet rf decks.

I am available most anytime to help with your questions.

73 Brent W1IA
Brent
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Re: E-rig

Postby JT - W6FO » Wed Oct 19, 2005 10:02 pm

Brent wrote:JT...the KD1J boards are no longer available.

Thanks for the reply Brent, but I am afraid your information is a bit inaccurate.

I purchased a set of boards from Kevin (KD1J) at the end of July and was just talking to him today and he still has plenty of boards available.

Unfortunately, I haven't had time to do anything with them yet. I've been insanely busy and the YL has just approved my plans to put up a small tower so I probably won't get to building a Class-E rig til winter. My new plans are definitely for a 10-FET rig as you suggest.

- JT
JT - W6FO
 
Posts: 7
Joined: Thu Jul 14, 2005 4:16 pm
Location: Canton, GA

Re: E-rig

Postby Brent » Fri Oct 21, 2005 4:35 pm

JT - W6FO wrote:
Brent wrote:JT...the KD1J boards are no longer available.

Thanks for the reply Brent, but I am afraid your information is a bit inaccurate.

I purchased a set of boards from Kevin (KD1J) at the end of July and was just talking to him today and he still has plenty of boards available.

Unfortunately, I haven't had time to do anything with them yet. I've been insanely busy and the YL has just approved my plans to put up a small tower so I probably won't get to building a Class-E rig til winter. My new plans are definitely for a 10-FET rig as you suggest.

- JT


Thanks for the update...I was under the impression earlier that he had abandon the project. I still suggest you use Steve's board.....it makes the design far easier. The new boards have a DC balance circuit included; negative peak limiter led etc....

Steve board provides for remoting the modulator fets which makes it more servicable. Also allows for 12 fets verses 8.
12 fets allow a magnitude of durability...if you develop a short in the rf deck, the modulator will survive without damage.

I am not being critical of Kevin's work....I still have his board operating with additional outboarded fets and they work fine, just difficult to service.

73 Brent W1IA
Brent
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